Avalanche Forecast

Two items should be on your mind Sunday if you head into the hills around Yakima and highway 12, new snow and sunshine. 

New snow: We don’t have any information about the snowpack structure in the East South, but if nearby locations like the Wenatchee Mountains are any guide, the snowpack is thin and weak. While this storm wasn’t a massive snow producer, most weather stations like Lost Horse and Bumping Ridge indicated 4-8” of new snow as of Saturday afternoon. Some areas could see a few more inches Saturday night. Easterly winds like redistibuted the snow onto S-W-N aspects at mid and upper elevations forming deeper pockets. Human triggered avalanches (including a remotely triggered slab) were reported on wind loaded slopes in the East Central zone, and you could find similar conditions in this region. Most of these avalanches failed at the interface of the old and new snow. This is a good time to dial it back. Choose simple terrain where its easy to identify and steer around slopes greater than 35 degrees.

A human triggered avalanche near Blewett Pass in the East Central zone Saturday. Diamond Head, NW 5200’, Photo: Adam Butterfield. 

Sun: Clouds should hang around the East South zone Sunday and you could even see a stray snow shower, but as things begin to dry out, the skies may begin to break. If the sun comes out, expect the snowpack to change and react differently. This will be a big change for the very cold and dry snow surface. You may notice this first when you see the snow shed from trees and rocks. When this occurs begin to think about loose avalanches on similar slopes. 

Prior to this storm numerous rocks, trees, stumps, and even bare ground could be found at mid and lower elevations. Travel slowly to give yourself time to react to some of these shallowly buried obstacles. 

March 12, 2020 (The regional synopsis is updated every Thursday @ 6 pm)

From March 6th to the 12th the Pacific Northwest experienced a few small storms and a few notable days for people and avalanches. Light to moderate snow accumulated slowly over a period of a few days, and avalanche danger increased from Low to Moderate over the weekend of March 8th. The exception was the West North zone, which won the snowfall competition this week. 18-24” of new snow was observed in the Mount Baker area on the 6th, and 10” of new snow on the 11th. Avalanche danger reached Considerable there for storm slab, wind slab, and loose wet avalanche problems. 

People, complicated avalanche terrain, and lots of avalanches. Bagley Lakes Basin, West North zone. Photo by Nathan Resick, March 8, 2020.

Loose dry slides initiated by skiers in big terrain. No one was caught or carried. East Central zone. March 8, 2020. Matt Primomo photo.

The snow fell with minimal wind, and accumulated slowly over firm suncrusts or wind stiffened surfaces. Thicker cloud cover inhibited the sun in areas where 4” to 12” of snow accumulated over the course of a few days. Cold overnight temperatures allowed the low density snow to weaken. By the 8th, the clouds broke up enough to allow strong radiation to change snow surfaces. When the sun finally did hit the snow, it quickly caused loose avalanches in steep terrain. 

An active weekend for people and avalanches: 

Many areas experienced some form of loose avalanche activity from March 6th to 9th.  Sunday, March 8th was the day that recorded the most widespread avalanche activity across the region. The size of these avalanches were directly related to the amount of new snow that had recently accumulated in that area, and the size of the terrain. 

West North zone on March 8, and West South zone on March 8th. Uphill and downhill tracks got covered by debris. Photos by Zack McGill and Dallas Glass.

We as a community can look back at, and learn from these few days. Numerous human triggered slides occurred, some were slabs but the majority were loose. A number of catch and carries were observed, and many more likely went undocumented. Luckily, no injuries or burials were reported. Observers across the region reported lots of instances where previous tracks got hit with debris, either from human triggered or natural avalanches. 

As the days get longer and folks begin to step into the alpine zone and bigger terrain more frequently, it is important to keep a humble attitude. Continuously evaluate route selection with potential for loose wet and cornice falls in mind. Check the mountain weather and avalanche forecasts for the most up to date info. Enjoy the backcountry, be safe, and let us know what you see out there!

-MP

Solo snowboarder aired into this slope, and went for a ride but was not buried or injured. Slide took out the corner of a skin track. Bagley Lakes Basin, March 8, 2020, Zack McGill photo.

Wind slab triggered by a skier at 7,500ft next to the popular route on Mt St Helens. The skier wasn’t caught or carried. Andy Goodwin photo, March 8, 2020.